Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Lausanne and University of Geneva, Rue Michel-Servet 1, 1211, Geneva, Switzerland.
Institut für Organische Chemie und Chemische Biologie, Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Strasse 7, 60438, Frankfurt, Germany.
Nat Commun. 2018 May 23;9(1):2032. doi: 10.1038/s41467-018-04110-1.
Modification of SMN2 exon 7 (E7) splicing is a validated therapeutic strategy against spinal muscular atrophy (SMA). However, a target-based approach to identify small-molecule E7 splicing modifiers has not been attempted, which could reveal novel therapies with improved mechanistic insight. Here, we chose as a target the stem-loop RNA structure TSL2, which overlaps with the 5' splicing site of E7. A small-molecule TSL2-binding compound, homocarbonyltopsentin (PK4C9), was identified that increases E7 splicing to therapeutic levels and rescues downstream molecular alterations in SMA cells. High-resolution NMR combined with molecular modelling revealed that PK4C9 binds to pentaloop conformations of TSL2 and promotes a shift to triloop conformations that display enhanced E7 splicing. Collectively, our study validates TSL2 as a target for small-molecule drug discovery in SMA, identifies a novel mechanism of action for an E7 splicing modifier, and sets a precedent for other splicing-mediated diseases where RNA structure could be similarly targeted.
SMN2 外显子 7（E7）剪接的修饰是一种经过验证的治疗脊髓性肌萎缩症（SMA）的策略。然而，尚未尝试采用基于靶点的方法来鉴定小分子 E7 剪接修饰剂，这可能会发现具有改善机制见解的新型疗法。在这里，我们选择茎环 RNA 结构 TSL2 作为靶点，该结构与 E7 的 5'剪接位点重叠。鉴定出一种小分子 TSL2 结合化合物，即同碳羰基托品嗪（PK4C9），它可增加 E7 剪接至治疗水平，并挽救 SMA 细胞中下游分子的改变。高分辨率 NMR 结合分子建模表明，PK4C9 结合 TSL2 的 pentaloop 构象，并促进向 triloop 构象转变，从而显示出增强的 E7 剪接。总的来说，我们的研究验证了 TSL2 作为 SMA 中小分子药物发现的靶点，确定了一种新型 E7 剪接修饰剂的作用机制，并为其他可能类似靶向 RNA 结构的剪接介导疾病开创了先例。
